Shape Healing hangs (or takes prohibitively long - at least more than a few minutes) on the shape that used to be processed in a matter of fraction of seconds.
The model is quickly processed in 6.6.0, 6.7.0, 6.7.1 and hangs in 6.8.0, 6.9.0.

a) Infinite cycle in BRepClass3d_SClassifier::PerformInfinitePoint(): it takes probing lines at random points across shape faces until it can classify the situation, but in this case this never happens because

b) due to incorrect computation of bounding box of a face in BndLib_Box2dCurve::Compute(), UV range returned by BRepTool::UVBounds() is reduced to zero by V, and intersector (IntCurvesFace_Intersector) fails to find intersection of that face by line. (The same happens for the opposite face that could save the situation if it worked...)